Contamination assessment,source apportionment and associated health risks of PTEs in agricultural soil under five land-use patterns in Sanya,China

To understand the levels of potentially toxic elements(PTEs)contamination in soils and their effects on human health from different agricultural land use in Sanya,China.128 soil samples(64 topsoil samples and corresponding subsoil samples)were collected from the five representative land-use patterns.Inductively coupled plasma mass spectrometry(ICP-MS),Atomic fluorescence spectrometry(AFS),and Inductively coupled plasma optical emission spectrometry(ICP-OES)were used to determine the content of PTEs(As,Cd,Hg,Cu,Cr,Ni,Pb,Zn,Co,Mo,Sb,and V).Correlation analysis and factor analysis were used to determine the source of PTEs.Geo-accumulation index(I_(geo)),hazard quotient(HQ),and total carcinogenic risk index(TR)were used to measure the PTEs contamination and its relative health impacts.Results showed that the average values of 12 PTEs in topsoil were higher than the Hainan soil geochemical baseline,showing different degrees of PTEs accumulation effect.The concentration of PTEs in the topsoil was lower than those in the subsoil except for Cd and Hg.The I_(geo)revealed that the major accumulated element in soils was As followed by Mo.Source apportionment suggested that parent materials and agricultural practices were the dominant factors for PTEs accumulation in the topsoil.Noncarcinogenic risks of soil samples from five land-use patterns presented a trend of paddy field>dry field>woodland>orchard>garden plot.However,the HQ values of 12 PTEs were less than the recommended limit of HQ=1,representing that there are no non-carcinogenic risks of PTEs for children and adults in the study area.The TR values are within 6.95×10^(-6)-1.38×10^(-5),which corresponds to the low level.Therefore the PTEs in the agricultural soil of the study area show little influence on the health status of the local population.

Temporal and Spatial Distribution of DIN and DIP Concentrations and Source Apportionment Along the Bohai Sea of China During 2015-2022

The Bohai Sea is one of the most polluted sea areas in China.In this study,we used 2184 integrated concentrations of dis-solved inorganic nitrogen(DIN)and dissolved inorganic phosphorus(DIP)in the Bohai Sea of China during spring(March,April,and May),summer(June,July,and August),and autumn(October and November)from 2015 to 2022 to explore the trends and sources of nutrients variations.From 2015 to 2022,DIN showed a downward trend until 2020 and then an upward trend,whereas DIP exhibited a stable trend with a slight decrease.The concentrations of DIN and DIP had similar seasonal pattern which was the highest in autumn(0.292±0.247 mg/L for DIN and 0.013±0.016 mg/L for DIP)but lower in spring(0.267±0.238 mg/L for DIN and 0.006±0.010 mg/L for DIP)and summer(0.263±0.324 mg/L for DIN and 0.008±0.010 mg/L for DIP).Sources of DIN and DIP apportioned by the positive matrix factorization(PMF)model were riverine input,sediment resuspension,sewage discharge,atmospheric deposition,and underground input.During 2015-2022,the largest contributor to DIN was sewage discharge(28.7%)and the largest contributor to DIP was sediment resuspension(44.6%).Seasonally,DIN in spring and autumn was dominated by sewage discharge(45.4%and 27.8%,re-spectively).Whereas in summer,it was dominated by riverine input(32.4%)and atmospheric deposition(29.7%).DIP was dominated by sediment resuspension during all three seasons(35.8%-52.5%).In addition,the increase in DIN concentrations in 2021 and 2022 were mainly due to the incremental input of river discharge and atmospheric deposition caused by increased precipitation during sum-mer and autumn.

Source apportionment of heavy metals in soils around a coal gangue heap with the APCS-MLR and PMF receptor models in Chongqing,southwest China

This study studied the characteristics and source apportionment of heavy metal pollution in the agricultural soil surrounding a gangue coal heap in Chongqing,China by using absolute principal component scores-multiple linear regression(APCSMLR)model and positive matrix factorization(PMF)model.The applicability of the models was compared in the assessment of source apportionment.The results showed that the average contents of Cd,Hg,As,Pb,Cr,Cu,Ni,and Zn in the surface soil were 0.46,0.14,9.66,31.2,127,95.6,76.0,and 158 mg/kg,respectively.Combined with the spatial distribution and correlation analyses,the results of source apportionment were consistent for both the APCSMLR and PMF models.Cd,Hg,As,and Pb were mainly affected by the gangue heap accumulation,with respective contributions of 74.6%,79.4%,69.1%,and 67.2%based on the APCS-MLR model and respective contributions of 69.7%,60.7%,57.4%,and 41.9%based on the PMF model.Ni and Zn were mainly affected by industrial and agricultural activities,while Cr and Cu were mainly affected by natural factors.The results of the source apportionment were approximately consistent between the APCS-MLR and PMF models.The combined application of the two receptor models can make the results of source apportionment more comprehensive,accurate,and reliable.

Source apportionment of river water pollution in a typical agricultural city of Anhui Province, eastern China using multivariate statistical techniques with APCS– MLR

The deterioration of the surface water environment has become a serious challenge for water resources management due to increasing anthropogenic disturbance. Water resources protection requires control of potential pollution sources. In this study, 99 water samples were collected from a river in a typical agricultural city of Anhui Province in eastern China, and these samples were analyzed in terms of pH, electrical conductivity, and the concentrations of F-, Cl-, SO42-, Na+, K+, Mg2+, Ca2+, As, Cr, Cu, Zn, and Pb. Cluster analysis, co-occurrence network analysis, and principal component analysis/factor analysis were conducted to qualitatively identify the potential sources of river water pollution in the study area. An absolute principal component score-multiple linear regression receptor model was used to quantitatively evaluate the contribution of each source to water quality parameters. The results showed that all observed water quality indices met the quality criteria specified in the Chinese drinking water standards, except for pH, ρ(F-), ρ(SO42-), and ρ(As). The heat map showed that the frequent recharge of pollutants from the tributaries during the wet season was the main reason for the deterioration of water quality. Five sources of river water pollution were identified, and their contribution ratios in a descending order were as follows: the geogenic process (24%) > agricultural activities (21%) > poultry farming sources (17%) > domestic pollution (9%) > transportation pollution (5%). Therefore, controlling pollution from agricultural activities, strengthening the regulation of livestock farming, and improving the sewage network are the recommended strategies for improving the quality of surface water resources in this area.

Long-term monitoring and source apportionment of PM_(2.5)/PM_(10) in Beijing,China

During 2001-2006,PM2.5 (particle matter with aerodynamic diameter less than 2.5 microns) and PM10 (particle matter with aerodynamic diameter less than 10 microns) were collected at the Beijng Normal University (BNU) site,China,and in 2006,at a background site in Duolun (DL).The long-term monitoring data of elements,ions,and black carbon showed that the major constituents of PM2.5 were black carbon (BC) crustal elements,nitrates,ammonium salts,and sulfates.These five major components accounted for 20%-80% of...

Characterization and Source Apportionment of Volatile Organic Compounds in Urban and Suburban Tianjin, China

Tianjin is the third largest megacity and the fastest growth area in China,and consequently faces the problems of surface ozone and haze episodes.This study measures and characterizes volatile organic compounds （VOCs）,which are ozone precursors,to identify their possible sources and evaluate their contribution to ozone formation in urban and suburban Tianjin,China during the HaChi （Haze in China） summer campaign in 2009.A total of 107 species of ambient VOCs were detected,and the average concentrations of VOCs at urban and suburban sites were 92 and 174 ppbv,respectively.Of those,51 species of VOCs were extracted to analyze the possible VOC sources using positive matrix factorization.The identified sources of VOCs were significantly related to vehicular activities,which specifically contributed 60％ to urban and 42％ to suburban VOCs loadings in Tianjin.Industrial emission was the second most prominent source of ambient VOCs in both urban and suburban areas,although the contribution of industry in the suburban area （36％） was much higher than that at the urban area （16％）.We conclude that controlling vehicle emissions should be a top priority for VOC reduction,and that fast industrialization and urbanization causes air pollution to be more complex due to the combined emission of VOCs from industry and daily life,especially in suburban areas.

Secondary organic carbon quantification and source apportionment of PM_(10) in Kaifeng, China

During 2005, the filter samples of ambient PM10 from five sites and the source samples of particulate matter were collected in Kaifeng, Henan Province of China. Nineteen elements, water-soluble ions, total carbon （TC） and organic carbon （OC） contained in samples were analyzed. Seven contributive source types were identified and their contributions to ambient PM10 were estimated by chemical mass balance （CMB） receptor model. Weak associations between the concentrations of organic carbon and element carbon （EC） were observed during the sampling periods, indicating that there was secondary organic aerosol pollution in the urban atmosphere. An indirect method of ＂OC/EC minimum ratio＂ was applied to estimate the concentration of secondary organic carbon （SOC）. The results showed that SOC contributed 26.2%, 32.4% and 18.0% of TC in spring, summer-fall and winter, respectively, and the annual average SOC concentration was 7.07 μg/m^3, accounting for 5.73% of the total mass in ambient PM10. The carbon species concentrations in ambient PM10 were recalculated by subtracting SOC concentrations from measured concentrations of TC and OC to increase the compatibility of source and receptor measurements for CMB model.

Distribution and Source Apportionment of Polycyclic Aromatic Hydrocarbons from Atmospheric Particulate Matter PM2.5 in Beijing

A total of 11 PM2.5 samples were collected from October 2003 to October 2004 at 8 sampling sites in Beijing city. The PM2.5 concentrations are all above the PM2.5 pollution standard （65 μg m^-3） established by Environmental Protection Agency, USA （USEPA） in 1997 except for the Ming Tombs site. PM2.5 concentrations in winter are much higher than in summer. The 16 Polycyclic aromatic hydrocarbons （PAHs） listed as priority pollutants by USEPA in PM2.5 were completely identified and quantified by high performance liquid chromatography （HPLC） with variable wavelength detector （VWD） and fluorescence detector （FLD） employed. The PM2.5 concentrations indicate that the pollution situation is still serious in Beijing. The sum of 16 PAHs concentrations ranged from 22.17 to 5366 ng m^-3. The concentrations of the heavier molecular weight PAHs have a different pollution trend from the lower PAHs. Seasonal variations were mainly attributed to the difference in coal combustion emission and meteorological conditions. The source apportionment analysis suggests that PAHs from PM2.5 in Beijing city mainly come from coal combustion and vehicle exhaust emission. New measures about restricting coal combustion and vehicle exhaust must be established as soon as possible to improve the air pollution situation in Beijing city.

A review of surface ozone source apportionment in China

Air pollution caused by particulate matter has significantly improved in China in recent years since the implementation of a series of stringent clean-air regulations.However,surface ozone concentrations have increased,especially in developed city clusters,such as the Beijing–Tianjin–Hebei,Yangtze River Delta,Pearl River Delta,and Sichuan Basin regions.Due to the complexity and nonlinearity of the ozone formation,accurately locating major sources of ozone and its precursors is an important basis for the formulation of cost-effective pollution control strategies.In this paper,the authors systematically summarize the reported results and outcomes of the methods and main conclusions of ozone source apportionment(regions and categories)in China from the published literature,based on observation-based methods and emission-based methods,respectively.The authors aim to provide a comprehensive understanding of ozone pollution and reliable references for the formulation of air pollution prevention policies in China.

Source apportionment and ecological risk assessment of PAHs in surface sediments from the Liaodong Bay,northern China

The sources and ecological risk from sixteen polycyclic aromatic hydrocarbons in surface sediment in the Liaodong Bay were investigated from 2014 to 2015.The total concentrations of PAHs ranged from 88.5 to 347.1 ng/g,and the high value occurred in the central region of the Liaodong Bay.Cluster analysis identified two site clusters representing the coastal region affected by land-based pollution and the central region of the Liaodong Bay.Principal component analysis-multiple linear regression and diagnostic ratios suggested that PAHs contaminants originated from a mixture of combustion and petroleum sources,and the major was combustion sources.Based on sediment quality guideline,naphthalene,acenaphthylene,acenaphthene,phenanthrene and dibenz[a,h]anthracene may occasionally cause adverse biological effects in some stations.The toxic equivalent concentrations of carcinogenic PAHs indicated low carcinogenic risk for the Liaodong Bay.The ecological risk and toxic pollution levels of PAHs were higher in the central region than in the coastal region along the Liaodong Bay.

Profiles and Source Apportionment of Nonmethane Volatile Organic Compounds in Winter and Summer in Xi’an, China, based on the Hybrid Environmental Receptor Model

Summer and winter campaigns for the chemical compositions and sources of nonmethane hydrocarbons(NMHCs)and oxygenated volatile organic compounds(OVOCs)were conducted in Xi’an.Data from 57 photochemical assessment monitoring stations for NMHCs and 20 OVOC species were analyzed.Significant seasonal differences were noted for total VOC(TVOC,NMHCs and OVOCs)concentrations and compositions.The campaign-average TVOC concentrations in winter(85.3±60.6 ppbv)were almost twice those in summer(47.2±31.6 ppbv).Alkanes and OVOCs were the most abundant category in winter and summer,respectively.NMHCs,but not OVOCs,had significantly higher levels on weekends than on weekdays.Total ozone formation potential was higher in summer than in winter(by 50%)because of the high concentrations of alkenes(particularly isoprene),high temperature,and high solar radiation levels in summer.The Hybrid Environmental Receptor Model(HERM)was used to conduct source apportionment for atmospheric TVOCs in winter and summer,with excellent accuracy.HERM demonstrated its suitability in a situation where only partial source profile data were available.The HERM results indicated significantly different seasonal source contributions to TVOCs in Xi’an.In particular,coal and biomass burning had contributions greater than half in winter(53.4%),whereas traffic sources were prevalent in summer(53.1%).This study’s results highlight the need for targeted and adjustable VOC control measures that account for seasonal differences in Xi’an;such measures should target not only the severe problem with VOC pollution but also the problem of consequent secondary pollution(e.g.,from ozone and secondary organic aerosols).

A new approach to spatial source apportionment of haze pollution in large scale and its application in China

Long-lasting expansion of haze pollution in China has already presented a stern challenge to regional joint prevention and control. There is an urgent need to enlarge and reconstruct the coverage of joint prevention and control of air pollution in key area. Air quality models can identify and quantify the regional contribution of haze pollution and its key components with the help of numerical simulation, but it is difficult to be applied to larger spatial scale due to the complexity of model parameters. The time series analysis can recognize the existence of spatial interaction of haze pollution between cities, but it has not yet been used to further identify the spatial sources of haze pollution in large scale. Using econometric framework of time series analysis, this paper developed a new approach to perform spatial source apportionment. We applied this approach to calculate the contribution from spatial sources of haze pollution in China, using the monitoring data of particulate matter(PM_(2.5)) across 161 Chinese cities. This approach overcame the limitation of numerical simulation that the model complexity increases at excess with the expansion of sample range, and could effectively deal with severe large-scale haze episodes.

Source Apportionment of Ambient PM_(10) in the Urban Area of Longyan City,China:a Comparative Study Based on Chemical Mass Balance Model and Factor Analysis Method

In order to identify the day and night pollution sources of PM10 in ambient air in Longyan City,the authors analyzed the elemental composition of respirable particulate matters in the day and night ambient air samples and various pollution sources which were collected in January 2010 in Longyan with inductivity coupled plasma-mass spectrometry（ICP-MS）.Then chemical mass balance（CMB） model and factor analysis（FA） method were applied to comparatively study the inorganic components in the sources and receptor samples.The results of factor analysis show that the major sources were road dust,waste incineration and mixed sources which contained automobile exhaust,soil dust/secondary dust and coal dust during the daytime in Longyan City,China.There are two major sources of pollution which are soil dust and mixture sources of automobile exhaust and secondary dust during the night in Longyan.The results of CMB show that the major sources are secondary dust,automobile exhaust and road dust during the daytime in Longyan.The major sources are secondary dust,soil dust and automobile exhaust during the night in Longyan.The results of the two methods are similar to each other and the results will guide us to plan to control the PM10 pollution sources in Longyan.

Application of Isotope Tracer Technique in Source Apportionment of Heavy Metal Pollution in Soil

The formation of heavy metal pollution in soil is closely related to human production and life. In order to effectively control heavy metal pollution and repair damaged soil,the pollution source should be known and judged first. Based on the preliminary analysis of major sources of soil heavy metal pollution in soil,combined with relevant literatures on heavy metal pollution source of soil or sediment at home and abroad in recent years,application progress of isotope tracer technique,especially lead isotope tracer technique,in the study of heavy metal pollution sources in soils and sediments were reviewed. The key points of future isotope tracer technology in the field of heavy metal pollution source apportionment were prospected.

Source apportionment of PM_(2.5)using PMF combined online bulk and single-particle measurements:Contribution of fireworks and biomass burning

Fireworks(FW)could significantly worsen air quality in short term during celebrations.Due to similar tracers with biomass burning(BB),the fast and precise qualification of FW and BB is still challenging.In this study,online bulk and single-particle measurements were combined to investigate the contributions of FW and BB to the overall mass concentrations of PM_(2.5)and specific chemical species by positive matrix factorization(PMF)during the Chinese New Year in Hong Kong in February 2013.With combined information,fresh/aged FW(abundant ^(140)K_(2)NO_(3)^(+)and ^(213)K_(3)SO_(4)^(+)formed from ^(113)K_(2)Cl^(+)discharged by fresh FW)can be extracted from the fresh/aged BB sources,in addition to the Second Aerosol,Vehicles+Road Dust,and Sea Salt factors.The contributions of FW and BB were investigated during three high particle matter episodes influenced by the pollution transported from the Pearl River Delta region.The fresh BB/FW contributed 39.2%and 19.6%to PM_(2.5)during the Lunar Chinese New Year case.However,the contributions of aged FW/BB enhanced in the last two episodes due to the aging process,evidenced by high contributions from secondary aerosols.Generally,the fresh BB/FW showed more significant contributions to nitrate(35.1%and15.0%,respectively)compared with sulfate(25.1%and 5.9%,respectively)and OC(14.8%and11.1%,respectively)on average.In comparison,the aged FW contributed more to sulfate(13.4%).Overall,combining online bulk and single-particle measurement data can combine both instruments’advantages and provide a new perspective for applying source apportionment of aerosols using PMF.

Atmospheric VOCs in an industrial coking facility and the surrounding area:Characteristics,spatial distribution and source apportionment

Industrial coking facilities are an important emission source for volatile organic compounds(VOCs).This study analyzed the atmospheric VOC characteristics within an industrial coking facility and its surrounding environment.Average concentrations of total VOCs(TVOCs)in the surrounding residential activity areas(R1 and R2),the coking facility(CF)and the control area(CA)were determined to be 138.5,47.8,550.0,and 15.0μg/m^(3),respectively.The cold drum process and coking and quenching areas within the coking facility were identified as the main polluting processes.The spatial variation in VOCs composition was analyzed,showing that VOCs in the coking facility and surrounding areas were mainly dominated by aromatic compounds such as BTX(benzene,toluene,and xylenes)and naphthalene,with concentrations being negatively correlated with the distance from the coking facility(p<0.01).The sources of VOCs in different functional areas across the monitoring area were analyzed,finding that coking emissions accounted for 73.5%,33.3% and 27.7% of TVOCs in CF,R1 and R2,respectively.These results demonstrated that coking emissions had a significant impact on VOC concentrations in the areas surrounding coking facility.This study evaluates the spatial variation in exposure to VOCs,providing important information for the influence of VOCs concentration posed by coking facility to surrounding residents and the development of strategies for VOC abatement.

Source apportionment and specific-source-site risk of quinolone antibiotics for effluent-receiving urban rivers and groundwater in a city, China

There is a large surface-groundwater exchange downstream ofwastewater treatment plants(WWTPs),and antibiotics upstream may influence sites downstream of rivers.Thus,samples from 9 effluent-receiving urban rivers(ERURs)and 12 groundwater sites were collected in Shijiazhuang City in December 2020 and April 2021.For ERURs,8 out of 13 target quinolone antibiotics(QNs)were detected,and the total concentration of QNs in December and April were 100.6-4,398 ng/L and 8.02–2,476 ng/L,respectively.For groundwater,all target QNs were detected,and the total QNs concentration was 1.09–23.03 ng/L for December and 4.54–170.3 ng/L for April.The distribution of QNs was dissimilar between ERURs and groundwater.Most QN concentrations were weakly correlated with land use types in the system.The results of a positive matrix factorization model(PMF)indicated four potential sources of QNs in both ERURs and groundwater,and WWTP effluents were the main source of QNs.From December to April,the contribution of WWTP effluents and agricultural emissions increased,while livestock activities decreased.Singular value decomposition(SVD)results showed that the spatial variation of most QNs was mainly contributed by sites downstream(7.09%-88.86%)of ERURs.Then,a new method that combined the results of SVD and PMF was developed for a specific-source-site risk quotient(SRQ),and the SRQ for QNs was at high level,especially for the sites downstream of WWTPs.Regarding temporal variation,the SRQ for WWTP effluents,aquaculture,and agricultural emissions increased.Therefore,in order to control the antibiotic pollution,more attention should be paid to WWTP effluents,aquaculture,and agricultural emission sources for the benefit of sites downstream of WWTPs.

Pollution characteristics and quantitative source apportionment of heavy metals within a zinc smelting site by GIS-based PMF and APCS-MLR models

The abandoned smelters present a substantial pollution threat to the nearby soil and groundwater.In this study,63 surface soil samples were collected from a zinc smelter to quantitatively describe the pollution characteristics,ecological risks,and source apportionment of heavy metal(loid)s(HMs).The results revealed that the average contents of Zn,Cd,Pb,As,and Hg were 0.4,12.2,3.3,5.3,and 12.7 times higher than the risk screening values of the construction sites,respectively.Notably,the smelter was accumulated heavily with Cd and Hg,and the contribution of Cd(0.38)and Hg(0.53)to ecological risk was 91.58%.ZZ3 and ZZ7 were the most polluted workshops,accounting for 25.7%and 35.0%of the pollution load and ecological risk,respectively.The influence of soil parent materials on pollution was minor compared to various workshops within the smelter.Combined with PMF,APCS-MLR and GIS analysis,four sources of HMs were identified:P1(25.5%)and A3(18.4%)were atmospheric deposition from the electric defogging workshop and surface runoff from the smelter;P2(32.7%)and A2(20.9%)were surface runoff of As-Pb foul acid;P3(14.5%)and A4(49.8%)were atmospheric deposition from the leach slag drying workshop;P4(27.3%)and A1(10.8%)were the smelting process of zinc products.This paper described the distribution characteristics and specific sources of HMs in different process workshops,providing a new perspective for the precise remediation of the smelter by determining the priority control factors.

Pollution characteristics and source apportionment of heavy metal(loid)s in soil and groundwater of a retired industrial park

Heavy metal(loid)s(HMs)pollution has become a common and complex problem in industrial parks due to rapid industrialization and urbanization.Here,soil and groundwater were sampled from a retired industrial park to investigate the pollution characteristics of HMs.Results show that Ni,Pb,Cr,Zn,Cd,and Cu were the typical HMs in the soil.Source analysis with the positive matrix factorization model indicates that HMs in the topsoil stemmed from industrial activities,traffic emission,and natural source,and the groundwater HMs originated from industrial activities,groundwater-soil interaction,groundwater-rock interaction,and atmosphere deposition.The sequential extraction of soil HMs reveals that As and Hg were mainly distributed in the residue fraction,while Ni,Pb,Cr,Zn,Cd,and Cu mainly existed in the mobile fraction.Most HMs either in the total concentration or in the bioavailable fraction preferred to retain in soil as indicated by their high soil-water partitioning coefficients(K_(d)),and the K_(d) values were correlated with soil pH,groundwater redox potential,and dissolved oxygen.The relative stable soil-groundwater circumstance and the low active fraction contents limited the vertical migration of soil HMs and their release to groundwater.These findings increase our knowledge about HMs pollution characteristics of traditional industrial parks and provide a protocol for HMs pollution scrutinizing in large zones.

Improving photochemical indicators for attributing ozone sensitivities in source apportionment analysis

Comprehensive Air Quality Model with extensions(CAMx)-Decoupled Direct Method(DDM)simulations of first-order ozone(O_(3))sensitivity to nitrogen oxides(NO_(x))and volatile organic compounds(VOCs)emissions were performed and combined with modelled P_(H_(2)O_(2))/P_(HNO_(3))ratios to obtain a range of thresholds for determining O_(3)-sensitivity regimes for different areas of China.Utilising the new threshold ranges for photochemical indicators,the method for determining O_(3)formation in the Ozone Source Apportionment Technology(OSAT)module within CAMx was improved by a dynamically varied threshold of P_(H_(2)O_(2))/P_(HNO_(3))ratio.The O_(3)concentration contributions in the newly added transition regime were apportioned to NO_(x)and VOCs emissions in proportion to the relationship between the P_(H_(2)O_(2))/P_(HNO_(3))ratio and first-order O_(3)sensitivity.The source contributions of O_(3)concentrations from different emission sectors from June to September 2019 were compared using the original and improved CAMx-OSAT.The results showed that the O_(3)concentration contributions changed significantly in the NO_(x)-limited regime,with a maximum decrease of 21.89%,while the contributions increased by up to 7.57%in the VOC-limited regime,and were within 15μg/m^(3)in the transition regime.The modified OSAT module enabled a more sophisticated attribution of O_(3)to precursor emissions and may have far-reaching implications for informing O_(3)pollution control policy.